The activation of the IFNβ induction/signaling pathway in porcine alveolar macrophages by porcine reproductive and respiratory syndrome virus is variable
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It has been recognized that the expression of type I interferon (IFNα/β) may be suppressed during infection with porcine reproductive, respiratory syndrome virus (PRRSV). This causes profound negative effects on both the innate and adaptive immunity of the host resulting in persistence of infection.
Test the effects of PRRSV infection of porcine alveolar macrophages (PAMs), the main target cell, on the expression of interferon beta (IFNβ) and downstream signaling events.
In order to examine those effects, PAMs harvested from lungs of healthy PRRSV-free animals were infected with virulent, attenuated, infectious clone-derived chimeric viruses, or field PRRS virus strains. Culture supernatants from the infected PAMs were tested for IFNβ protein expression by means of indirect ELISA and for bioactivity by a vesicular stomatitis virus plaque reduction assay. The expression of the Mx protein was assayed to ascertain signaling events.
These experiments demonstrated that PRRSV does induce variably, the expression of bioactive IFNβ protein in the natural host cell. To further elucidate the effects of PRRSV infection on IFNβ signaling, Mx-1 an interferon stimulated gene (ISG), was also tested for expression. Interestingly, Mx-1 expression by infected PAMs generally correlated with IFNβ production.
The results of this study demonstrate that the induction of IFNβ and signaling in PAMs after PRRSV infection is variable.
KeywordsPorcine reproductive respiratory syndrome virus Interferon beta Mx-1 innate immunity
This work was supported by funds from the Specific Cooperative Agreement #58-1940-2-245 between the University of Connecticut and the USDA, ARS, USDA grant # 20043520414267, Integrated Control and Elimination of PRRS (NC229), Storrs Agricultural Experiment Station, University of Connecticut. The authors thank Drs. F. Osorio and A. Pattnaik (University of Nebraska, Lincoln, NE) for providing the chimeric viruses used in this work. The authors also thank Dr. Surya Waghela (Texas A&M University, College Station, TX) for valuable suggestions with the manuscript.
C. Overend performed most of the experimental work and prepared the manuscript. J. Cui performed the statistical analysis and graphs. M. Grubman served as scientific collaborator and consultant, reviewed the data and the manuscript. A. Garmendia directed the study, contributed in the experimental work, reviewed the data and the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare no conflict of interest
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